Sound reproducing and amplifying system



Sept. 14, J F E L SOUND REPRODUCING AND AMPLIFYI-NG SYSTEM original Filed May 10, 1927 2 Sheets-Sheet l INVENTOR. %T Q x M w Y Jar/1v [4164f ATTORNEY.

Sept. 14, J F. ENGLE SOUND REPRODUCING AND AMPLIFYING SYSTEM Original Filed May 10, 1927 2 Sheets-Sheet 2 ATTORNEY.

Patented Sept. 14, 1937 UNITED STATES PATENT OFFICE SOUND REPRODUCING AND AMPLIFYING SYSTEM John F. Engle, Lakewood, Ohio 3 Claims. (Cl. 179-1) One particular embodiment of my invention is shown and described in my application for Letters Patent Serial No. 190,153, filed May 10, 1927, now Patent No. 1,789,700, granted Jan. 20, 1931, of which this is a division.

My invention relates to apparatus and methods for reproducing clearly and without distortion music, speech and other sounds received by radio, and from phonograph records, from records or films, or in any other manner, and relates more particularly to receiving the sounds on a. plurality of receiving and reproducing devices, each adapted to a range or band of audio frequencies, and combining the sounds so received.

Diaphragms, horns, cones and other reproducing devices are, in general, adapted to reproduce best sounds of a particular frequency or of a limited range of frequencies, and sounds falling outside such a range of frequencies are either not reproduced at all or are inadequately reproduced, and received speech and music are therefore distorted.

I have found that by using a plurality of sound reproducing devices, especially in connection with corresponding receiving'circuits, I can reproduce speech, music or any other sounds, covering any desired range of frequencies, with entire fidelity.

In the accompanying drawings I have shown, in diagrammatic form, embodiments of my inventions.

Fig. 1 shows a radio receiving set having a plurality of audio-frequency'circuits in parallel, each circuit having a corresponding loud speaker.

Fig. 2 shows a phonograph, such, for instance, as is employed in the so-called vitaphone, arranged for reproducing with a plurality of circuits with loud speakers in parallel.

Figure 3 gives a front view and Figure 4 gives a side view of a double diaphragm with a plurality of speaker units.

In Fig. l, J is an antenna, connected through the condenser C and the primary coil of radiofrequency transformer M to ground G. V and V are vacuum tubes; each containing a filament, a grid and a plate, as shown, in the radio frequency amplifying stages of the receiving set, and M and M are radio frequency transformers. V V and V are detector vacuum tubes, and V V V V V and V are vacuum tubes in the audio frequency amplifying stages of the set. T,

T T T, T and T are audio frequency transformers. T and '1 contain considerable iron and possess high impedance and are adapted to pass a band of low frequency audio vibrations,

I! and '1' contain less iron and possess less impedance and are adapted to pass a band of intermediate frequency audio vibrations. T and '1 contain only a. small amount of iron and possess the least impedance, and are adapted to 5 pass a band of high frequency audio vibrations. S, S and S are loud speakers, S being tuned to a low frequency band of audio vibrations, S being tuned to an intermediate frequency band of audio vibrations, and S being tuned to a high frequency band of audiovibrations, and these loud speakers are connected, respectively, to the corresponding audio frequency circuits, as shown.

C C and C are variable condensers; C C C and C" are fixed condensers; ,R, R R R and R." are variable resistances; R R and R are resistances; and L is a grid leak. The filament battery terminals are shown at A- and A+; and the plate battery terminals at B- and B+v and B+90 v.

In this diagram three parallel circuits are shown, but two, four or more parallel circuits can be used where circumstances make it desirable. Also, the main circuit can be split or sub-divided at any point desirable to meet different conditions. For example, the main circuit can be divided after the last audio stage and through the speakers only, or between the first and second audio stages, or between the detector tubes and the first audio stage, or at some other point, the division even reaching back one or two stages into the radio frequency stages.

Fig. 2 shows the application of my system to reproducing music, speech and other sounds from a vitaphone or phonograph record with an electric, pickup. D represents a phonograph record, E an electric pickup, andT an audio frequency transformer. Connected to the secondary of this transformer there are three circuits in parallel,

each with appropriate filtering and amplifying apparatus as indicated. Corresponding loud speakers, S S and S are connected with the respective circuits. The upper circuit in this figure is designed to pass a band of audio frequencies of relatively high pitch and the speaker S is tuned so asto respond to this same high frequency band.' The middle circuit is designed to pass an intermediate band of audio frequencies and the loud speaker S is correspondingly tuned. The lower circuit is designed to pass a band of frequencies of deeper pitch and the loud speaker S is constructedto reproduce these lower tones most effectually.

The number of circuits and corresponding loud speakers may be two, three, or more, depending upon the circumstances of each case, and the type of circuit, the number of filters and ampli-e fiers, and the kind of loud speakers may be varied. For instance, the audio circuits shown in 5 Fig. 1 may be used.

In the practice of my invention with the system of sound reproducers, any suitable form of electric pickup may be employed, and the currents therefrom may be amplified before reaching the transformer or the multiple circuits. When phonographs are used without an electric pickup, the sound waves from the needle diaphragm or other mechanical pickup should be converted into electric currents through microphones or otherwise, unless the sound waves are led directly to a plurality of variously tuned loud speakers. My method and apparatus can also be applied to systems where the sound record is on a film, with or without phonographs.

In Figs. 3 and 4 of my original application, H and H are diaphragms, supported in a frame F, and connected by a sound post P. Speaker units are attached to diaphragm H at 0, O 0 and 0 With the -sound post and the speaker units as shown, the diaphragm H is divided up into unequal areas having different natural frequencies, each area, by means of its corresponding speaker unit, being connected to a corresponding amplifying circuit of approximately the same frequency. The sound post P will then transmit the waves which are the resultant of vibrations of all the areas of H to the second diaphragm H which will further amplify the sounds, and will modify their quality according to its dimensions and the material of which it is composed. These diaphragms can be made of any suitable material and of any appropriate shape, depending upon the circumstances of each case. There can also be attached to one or'both of these diaphragms gongs or other shapes of resonant material to modify its, or their, quality further, or weights or mutes can be used for the same purpose. These diaphragms can be employed in my system instead of several separate loud speakers.

In the embodiments of my invention shown in the figures, each of the parallel circuits is broadly tuned to a band of frequencies, or has filters which pass such a band of frequencies, and the corresponding loud speaker is broadly tuned to the same band of frequencies. The'loud speakers operate simultaneously, so that their combined output reproduces the whole range of audio frequencies received at a station, or produced on a phonograph, or otherwise, with equal clearness and intensity. They may be made of various materials to impart the desired true quality or color. The number of parallel circuits and loud speakers can.be varied to suit circumstances, and the closeness of their tuning can be varied; generally speaking, the tuning bands will be narrower, the greater the number of circuits and loud speakers.

The tuning of the circuits can be accomplished in any suitable manner, by the use of impedances, inductances, capacitances and resistances. Where transformer coupling is employed, the transformers in each circuit may be so designed as to pass most readily the band of frequencies sired to reproduce, and upon other ClI'CllIIlStdI'lCGS of each case.

In arrangements such as shown in Fig. 1, as many stages of amplification as desired may be used, and each stage may be tuned, or have filters, and any suitable kind of coupling may be employed. In arrangements such as shown in Fig. 2, the transformer between the record circuit and the parallel audio stages maybe omitted, and all but one of the filters or other tuning devices in each circuit may be omitted, and in general I do not confine myself to the exact constructions shown in the-drawings and described herein, but what I claim as my invention and desire to secure by United States Letters Patent is:

1. A sound reproducing system, having a plurality of circuits in parallel each constituting a split up from the main circuiteach derived from said main circuit by a sub-division of the detector-plate circuit and each of the derived parallel circuits having characteristics covering a range of audio-frequency separate from the other circuit, each circuit comprising filters first diifering from each other confining each circuit to a predetermined frequency band, and each circuit thereafter having audio-frequency .transformers of diflerent characteristics in each of the circuits. y

2. In a sound reproducing system, a source of radio frequency, a plurality of loud speakers each clearly responsive to different frequency bands, a separate audio-frequency circuit connected with each of said loud speakers, said individual separated circuits each derived from a main circuit by a sub-division of the detector-plate circuit, a plurality of audio-frequency transformers or amplifiers having different characteristics for each band and each group specifically suited to the particular range of frequencies in the band for which its loud speaker is attuned.

3. A sound reproducing system comprising a plurality of independent circuits each for a separate band of audio-frequency vibrations, a main delivery circuit divided into a plurality of circuits derived from said main delivery circuit by a sub-division of the detector-plate in said circuit and each covering a range or band leading first to a separate filter for each of the independent circuits, said independent circuits each having in order a plurality of amplifying transformers different in characteristics respectively for the different circuits, and connected to a loud speaker adapted to emit audible fundamental tones and overtones.

' JOHN I". ENGLE. 

